This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Simian varicella virus (SVV) infection of primates shares clinical, pathological, immunological and virological features of varicella zoster virus (VZV) infection of humans. Latent SVV infection can be established in cynomologous or African green monkeys (AGM) by exposing SVV-seronegative monkeys to an SVV infected cage-mate monkey. This year we conducted portions of three experiments with AGMs. Two groups were latently infected with simian varicella virus (SVV) and treated for possible reactivation utilizing two different treatments. Animals GV . were only irradiated with a single dose (200cGy of X-rays, animals HC were were irradiated with a single dose (200 cGy) of X-irradiation and then treated with tacrolimus (80-300 mg/kg/day). The third group of animals were group housed and one animal from every group acutely infected with SVV. This group passed the acute phase and is in the process of developing latency. In three months, this final group will undergo irradiation, as described above, and be given daily treatment with the immunosuppressive drug, prednisone (1 mg/kg/day), as a possible trigger of virus reactivation. Samples taken are being analyzed for virus load, histopathological changes and evidence of SVV reactivation.